The present invention relates to a permanent-magnetic field armature, in short permanent-field armature for an electrical machine and also to an electrical machine with such an armature and to a method for manufacturing the armature.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Permanent magnet-field electrical machines have a rotor structure in which the magnets are disposed inside the rotor, which is also referred to as IPM construction (IPM—Interior Permanent Magnet). To this end slots or magnet pockets are provided in the rotor laminated core in which the permanent magnets are disposed. Rotors or this type are especially robust mechanically because the internal permanent magnets are protected from mechanical influences.
In an armature with interior magnet pockets, i.e. a rotor for example, the problem arises that, to guide the magnetic flux between the armature surface and the interior magnet pockets a soft-magnetic material should be used in the armature body. However a magnetic short circuit within the armature body can also be produced by such a soft magnetic material, so that the magnetic excitation of the permanent magnets cannot be used for driving the armature. This magnetic short circuit is also referred to as leakage.
To address this problem, the provision of so-called flux inhibitors in the rotor body has been proposed. These flux inhibitors can be embodied between the interior magnet pockets and be hollow spaces filled with air for example. The disadvantage here is that such hollow spaces destabilize the rotor body mechanically.
It would be desirable and advantageous to provide an improved permanently excited armature of an electrical machine to obviate prior art shortcomings and to reduce a magnetic short circuit of the magnetic field of the permanent magnets within the armature body.